Cutting thermal insulation batts is a very difficult and awkward task even for professional installers of this material. Very early cutters for insulation batts were nothing more than a very large pair of scissors or a conventional utility knife.
U.S. Pat. No. 5,075,974 granted to Edward Mcllhaten on Dec. 31, 1991, discloses a substantial improvement in a cutting tool for use on insulation batts. The cutting tool comprises a utility knife housing, having a razor-type cutting blade, extending from one end thereof. The elongated housing is seated in a "U" shaped cradle that is attached to two parallel rods.
The parallel rods terminate in guide rings, near the end of the knife housing that carries the cutting blade. The parallel rods are reversely curved to form a spring system that includes a wire-like posts, extending upwardly through the above-mentioned guide rings. The spring system can be positioned against a batt of insulation to exert a compressing action on the fibrous batt material when a downward manual pressure is exerted on the knife housing. During downward motion of the knife housing, the guide rings slide down on the parallel posts, for the purpose of ensuring a true vertical motion of the knife housing. After the insulation batt has been compressed, the knife housing can be drawn across the batt surface so that the razor blade cuts through the compressed bat thickness.
U.S. Pat. No. 5,325,594 issued on Jul. 5, 1994, discloses a simple attempt at providing a batt insulation cutting tool. This tool is nothing more than a thick sheet of transparent plastic material, e.g., plexiglass, curved into a "C" shaped cross-section (when viewed along the edge of the sheet). Opposite ends of the curved plastic sheet have openings therein that fit around, or over, end areas of a conventional utility knife. This device does not provide much of a mechanical advantage to compress the batt. Nor does it provide much in the way of safety. No structure acts as a protective blade guard.